Method and apparatus for a speed-adjustable conveyer-type dryer



March 22, 1966 A. G. LAVENDER 3,241,249

METHOD AND APPARATUS FOR A SPEED-ADJUSTABLE YER CONVEYER-TYPE DR 2 Sheets-Sheet 2J Filed Jan. 24, 1963 III ubrqg G. Lavender INVENTOR.

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United States Patent O M' 3,241,249 METHOD AND APPARATUS FOR A SPEED-AD- JUSTABLE CONVEYER-TYPE DRYER Aubrey G. Lavender, 824 NW. Evans St., Sheridan, Oreg. Filed Jan. 24, 1963, Ser. No. 253,725 10 Claims. (Ci. 34--25) This invention relates to conveyer-type dryers, and more particularly to such dryers with means whereby adjustments may be made in the speed of the conveyer in the dryer, thus to change the nal moisture contents of articles transported thereon. A specic embodiment of the invention concerns veneer dryers, having one or more power-driven conveyer decks therein, with means controlling the speed of such decks whereby veneers of the desired dryness may be obtained. While describing the invention in connection with veneer dryers, it is appreciated that certain aspects of the invention are applicable to other types of dryer apparatus. A

The invention includes not only a novel means for changing the speed of a dryer, but also a method, whereby articles (such as veneer sheets) may be handled in a dryer with maximum production of sheets of suitable dryness resulting.

Thus, a general object of the invention is to provide novel means for controlling the movement of a conveyer in a conveyer-type dryer, whereby its speed may be changed thus to change the degree of dryness obtained in articles transported thereon.

More specically, an object is to provide means for controlling the speed of a conveyer in a dryer, which relies upon testing, at regular intervals, the moisture content of articles handled, and totalizing the results obtained in the tests with total results determining appropriate change in the conveyer speed.

Another object is to provide a method of handling articles in a dryer, such as sheets of veneer, where the sheets are divided into a series of sample batches, and the moisture content of successive sheets in each batch is determined, with appropriate change made in the speed of the conveyer in the dryer, when it is determined that the proportion of relatively wet sheets is above or below that desired for maximum dryer production.

Veneer, after it has been cut from a log, is relatively wet. Further, two dilerent veneer pieces may have quite different moistures, even when they are cut from the same log. Thus it is not uncommon to find, in sapwood portions of a log, moistures ranging up to about 200%, based upon the dry wood weight, whereas portions of the heartwood within the same log may have moistures of only 25%, based on dry wood weight. Prior to producing plywood or other products from a series of veneer pieces, the veneer is sent through a dryer, where the moisture in all pieces is substantially reduced. If all veneer pieces were substantially completely dried, then their final moisture contents would be substantially uniform.

It would be possible, of course, to dry all the veneer pieces in a series treated so that the moisture content of the wettest pieces is below a given desired value, say This would tend to produce uniformity in dryness. However, such drying would have the disadvantage of making the veneer dryer relatively unproductive. This is because of the very slow speed that would be required in the conveyer or conveyers of the dryer if the exceptionally wet piece of veneer in a series of pieces is to be suitably dried.

This invention recognizes that there is considerable variation in the moisture contents of dierent pieces of veneer, and that maximum dryer production results if a dryer speed is selected where a substantial proportion, but not all, of the veneer pieces in a series are dried to suitable dryness. Those pieces that travel through a dryer 3,241,249 Patented Mar. 22, 1966 and still have excessively high moisture contents mayv then be redried, to bring their moisture contents within the desired range. Such operation of a dryer permits a faster dryer speed, with suitable drying of all but the exceptional pieces of veneer. This in turn results in greatest over-all dryer production.

According to this invention, it is iirst established that for maximum dryer production in a given sample batch of veneer pieces, a certain percent of the pieces should pass through the dryer without being sutiiciently dried. A dryer speed is then selected which is found to produce this percentage of overly wet pieces. Successive `pieces of veneer, in recurrently selected sample batches of veneer, are tested, as the pieces approach the end of the dryer, to determine the amount of moisture in the pieces. If it is found that in a sample batch the percentage of wet pieces is dropping below that desired, the dryer speed is increased. Conversely, if it is found that the percentage of wet pieces is above that desired, the dryer speed is decreased. This is done automatically, and continuously, as veneer travels through the dryer.

Thus, another object of the invention is to provide means for regulating a conveyer-type dryer, which includes moisture-detector means, operable to classify successive veneer pieces or sheets as wet or dry (depending upon their moisture content), sensor means sensing the number of sheets that move through the moisture-detector means, and means for controlling conveyer speed responsive to the proportion of wet to dry pieces determined to have passed through the dryer by said moisture-detector means and said sensor means.

An object related to the above is to provide a dryer with means for controlling its operation, which includes a reversible control motor for regulating the speed of the conveyer therein, and electrically operated control devices controlling the reversible control motor, such control devices in turn being controlled by a moisture-detector means and a sheet-sensor means, as indicated above.

Yet another object of the invention is to provide a novel method of drying articles, such as veneer pieces, which comprises recurrently testing batches of the articles for dryness, each batch contaning a plurality of the articles (and the ytesting of each batch comprising; testing successive articles in the batch), and making appropriate change in dryer speed depending upon the proportion of wet to dry articles found to occur in the batches tested.

A still further object of the invention is to provide means for regulating the conveyer in a. conveyer-type dryer, which results in proper control of dryer speed, and which does this in a highly practical and satisfactory manner.

These and other objects and advantages are attained by the invention, and the same is described hereinbelow in conjunction with the accompanying drawings, wherein:

FIG. 1 illustrates, somewhat schematically, portions of a conveyer in a deck of a conventional veneer dryer, portions of a motor-operated means for moving the conveyer, and portions of a control means provided for controlling the speed of the conveyer through adjustment of said motor-operated means; and

FIG. 2 illustrates, diagrammatically, a control circuit as contemplated by an embodiment of this invention, such being part of the control means partially shown in FIG. l, operable automatically to cause adjustment of the motoroperated means shown in FIG. 1, with such adjustment being related to the percentage of wet to dry pieces moving through the dryer.

Referring now to the drawings, and first of all to FIG. 1, 10 indicates portions of a conveyer in one of the decks 0 of a conventional type of veneer dryer 9. The entire gated conveyer decks of the type shown (typically five or six) which extend through an enclosed heated chamber. On use of the dryer, veneer pieces are deposited continuously on the various decks, and such travel one after another to the discharge end of the dyer, where the veneer is removed. On traveling through the dryer, moisture in the veneer is removed.

The portions of the conveyer shown comprise a lower set of rolls 12 journaled on a frame 13 for the dryer, which are rotated under power by means of a chain 14. The latter is trained over sprockets secured to one set of ends of rolls 12. The conveyer also includes upper rolls 15, which are gravity rolls, and which press veneer downwardly on lower rolls 12. Drive is transmitted from the lower rolls to the upper rolls, by gears, such as gears 16 and 18.

With further reference to FIG. 1, power-operated means for rotating the rolls of the conveyer is provided, comprising a drive motor 20 with its output shaft operatively connected through chain 22 to the input shaft of an adjustable speed gear box 24. The output shaft of gear box 24 is connected, through chain 26, to rolls 12. Adjustable speed gear box 24 includes an adjusting shaft 28, equipped with a sprocket 30. Shaft 28 may be rotated in one direction, to increase the ratio of the speed at which chain 22 moves to the speed at which chain 26 moves. Rotation of shaft 28 in the opposite ydirection decreases the ratio of the speed at which the two chains move.

The left end of conveyor in FIG. l represents the off-bearing end of the conveyer. Mounted on frame 13 of the dryer adjacent its off-bearing end is a conventional moisture detector 34. Detector 34 includes the usual electrically operated means for detecting the moisture of sheets passing thereover. Mounted on the dryer frame above the moisture detector is a sensor or sensing means 37 (a switch finger) actuating a switch 36. A piece of vencer passing through the dryer and under the switch nger raises the switch finger to close switch 36. On the veneer pieces passing beyond the switch linger, the finger drops and switch 36 opens. Thus, the sensor is actuated each time that a veneer piece passes thereunder.

In the operation of the dryer, according to this invention, a veneer piece on passing the switch finger actuates switch 36, and this switch in turn actuates means that counts the times finger 37 is actuated (or the number of pieces passing under finger 37). The moisture detector also actuates a counting device, which counts the number of pieces passing the detector which are wet; i.e., have moistures above a previously determined satisfactory moisture level (which for purposes of illustration might be considered as 6%, based on the dry weight of the Wood). After a sample batch of sheets have passed the sensor and detector, and the total number of such sheets in the batch as well as the number of wet sheets in the batch have been counted or recorded, gear box 24 is adjusted to speed up or slow down the conveyer in the dryer. In those cases where the number of wet sheets in the total number of sheets in the batch is found yto be below the number desired, the conveyer is speeded up. If the number of wet sheets is too great, the conveyer of the dryer is slowed down.

Referring now to FIG. 2, here a control circuit is illustrated which performs the control function above indicated. The circuit comprises, in general, two stepping relays (indicated at S0 and 52) that operate together to count out successive pieces of veneer as 4they travel through the dryer7 until a sample batch has been counted. These then are reset and count out another sample batch (the stepping relays operating recurrently). Also part of the circuit is a third stepping relay S4, connected to the moisture detector, and operable to count out veneer pieces in a sample batch passing the detector `that the detector determines are wet.

In FIG. 2, it will be seen that sensor or switch linger 37 of switch 36 is operable, when 1t closes switch 36 (by a piece of veneer passing thereunder), to complete a circuit from a source conductor L2, through a conductor 56, a solenoid a of stepping relay 50, conductors 58, 59, normally closed switch a of a relay 60, conductor 61, a norm-ally closed switch 63a of a time-delay relay 63, a conductor 65, a normally closed switch 67a of a timedelay relay 67, to a source conductor L1. With energizing of solenoid 50a of stepping relay 50, movable arm 50h of the stepping relay (shown in FIG, 2 in its starting position) is advanced one contact, along the series of electrically joined contacts 50c provided in the stepping relay. Upon the piece of veneer that has actuated finger 37 passing beyond the finger, switch 36 opens. When a subsequent veneer piece again passes under the finger to close again switch 36, solenoid 50a is energized in a similar lmanner, with advancement of arm 50h in stepping relay 50 one more contact along the series of joined contacts 50c. Stepping relay 50 in this manner counts out the pieces of veneer passing switch linger 37.

With arm Sb of the stepping relay engaging any of the electrically joined contacts 50c in the relay, line conductor L2 is connected through movable arm 50h, one of the contacts 50c, a conductor 70, the solenoid of a relay 72, and a conductor 74, to a contact 54e of stepping relay 54. With the movable arm 54!) of stepping relay 54 in the starting position shown in FIG. 2, contact 54d is electrically isolated from line conductor L1. Thus advancement of arm 50h in relay 50 along the joined contacts 50c produces no change in the circuit, with the parts as illustrated.

On contact arm Silb in stepping relay 50 advancing the limit of its travel, or into its actuating position, the arm engages a contact 50d. This occurs after enough closings of switch 36 to advance arm Stb beyond the electrically joined contacts 50c. For explanation purposes, it will be assumed that 35 actuations of switch 36 are required for arm Slb to advance into engagement with contact 50d. (In FIG. 2, stepping relay 50 has been shortened, with removal of many of the contacts 50c, for reasons of simplicity.) With contact arm 50b engaging contact 50d, a closed circuit is produced from line conductor L2, through the stepping relay, conductor 76, a conductor 78, the solenoid of a relay 6l), conductors 82, 61, normally closed switches 63a, 67a, to line conductor L1.

This results in energizing of the solenoid of relay 60, and closing of its switches 6tib and 60C, and opening of its switch 60a. With opening of switch 60a, any energizing of solenoid 50a of stepping relay 50 is prevented, which places the stepping relay in condition to be reset (by return of arm 56h to its starting position). With closing 0f switch 66h, a circuit is completed from line conductor L1, through the switch, conductor 80, and solenoid Sile of stepping relay 50, to line conductor L2, causing energizing of solenoid 56e. Solenoid 50e is the resetting solenoid for relay 50, and when energized, it shifts contact arm Stbb back to its starting position. Switch 60C -of relay 60 produces a holding circuit for the solenoid of relay 60, from line conductor L1, through normally closed switches 67a, 63a, conductor `61, conductor 82, the solenoid of relay 60, conductors 78, 84, switch 60C, conductors 38, 90, 56, and switch 36, to line conductor L2. On the veneer piece that first caused energizing of the solenoid of relay 60 passing beyond switch finger 37, the solenoid of relay 611 de-energizes.

At the same time that resetting solenoid 50e of the stepping relay is energized (by closing of switch 60h) a circuit is completed from line conductor L1, through switch 60h, conductor 91, closed switch 72b, conductor 92, and solenoid 52a of stepping relay 52, to line conductor L2. This energizes solenoid 52a of stepping relay 52, and causes its movable Contact arm 521; to be advanced along one of the electrically isolated contacts 52C in the steplping relay. Thus it will be seen that stepping relay 52 has its arm advanced one position each time that the contact arm of stepping relay 50 completes a pass from its starting to its actuating positions.

Stepping relay 52, in addition to the three electrically isolated contacts 52C shown, has another pair of contacts, indicated at 52j and 52g, respectively. After three complete passes by contact arm 50b of relay 50 (and in the absence 4of actuation of other parts of the circuit, as will be described below), arm 52b of relay 52 is advanced to a position engaging contact 521. This completes a circuit from line conductor L2, through the movable arm of relay S2, the solenoid of a relay 94, conductor 96, arm 54b of stepping relay 54, to line conductor L1. As a result, the solenoid of relay 94 is energized, and its normally open switch 94a closes. As will be hereinafter described, upon closing of switch 94a, circuitry is actuated which causes speeding up of the conveyer in the dryer.

Somewhat by way of summary, upon completion of three complete passes` of contact arm 50h of stepping relay 50 (or after 105 veneer pieces have passed the switch finger 37), and if nothing else has happened (as by the detector noting the presence of wet boards), then movable arm 5217 produces energizing of relay 94, and (as will be described) speed-up in dryer speed. Stepping relays 50, 52 thus function to count out 105 pieces of veneer, and, under the conditions stated, then produce speed-up in the dryer.

As already indicated, the passage of wet pieces of veneer across the moisture detector also produces changes in the circuit, and this portion of the invention will now be described.

For purposes of explanation, it will be assumed that veneer pieces with over 6% moisture are wet veneers needing redrying, and veneer pieces with less than this moisture are satisfactory, or dry veneers. With such operating conditions, moisture detector 34 is operable to close a switch 34a, whenever the detector notes a veneer piece with over 6% moisture, i.e., a wet veneer piece. (The usual mechanism would be included, that is operated by the detector, to mark a veneer which is wet, enabling the wet veneers to be separated out when they leave the dryer.)

Assuming now that such a wet veneer piece passes the moisture detector, this wet piece simultaneously produces closing of switch 36 (by actuating linger 37), and closing of switch 34a. This completes a circuit from line conductor L2, through switch 36, conductor 56, conductor 90, conductor 100, solenoid 54]c of stepping relay 54, conductor 102, now closed switch 34a, through conductors 58, 59, and normally closed switches 60a, 63a, and 67a, to line conductor L1. At the same time, a circuit is completed from line conductor L2 to line conductor L1, through conductor 90, the solenoid of a relay 106, and conductor 104 (the solenoid of relay 106 being electrically in parallel to solenoid 54j). With a circuit completed to the solenoid of relay 106, the solenoid energizes, and switch 106a of the relay closes. Switch 106:1 serves to keep solenoid 54f in an energized state should switch 34a open. With solenoid 54f energized, movable contact arm 54h of stepping relay 54 advances along one of the electrically joined contacts 54C in the stepping relay.

After the wet veneer piece passes beyond finger 37 and the moisture detector, the circuits for solenoid 54jc and relay 106 open. Another wet veneer piece passing the moisture detector produces a further advance of the movable contact arm -54b. Thus, stepping relay 54 is operable to count the number of wet boards passing the moisture detector.

In stepping relay 54, there are, besides the four electrically joined contacts 54C illustrated, an electrically isolated contact 54d, and another contact 54e. On tive wet boards passing the moisture detector, movable contact arm 54b engages contact 54e, thus to connect line conductor L1 through conductor 74 with the solenoid of relay 72. The solenoid of relay 72 is connected through conductor 70 and movable contact arm 50b of stepping relay 50 to line conductor L2 (with the movable contact arm 5011 in any `of its positions save its nal actuating position). Thus with arm 54h engaging contact 54e, the solenoid of relay 72 is energized, producing closing of switches 72a, 72b in the relay. When this occurs circuitry is actuated which causes a slowing down in dryer speed, as will be hereinafter described.

The mechanism counting successive veneer pieces moving through the dryer (in batches of and the -mechanism counting the wet veneer pieces have been described. The means whereby these mechanisms produce appropriate change in dryer speed will now be discussed.

Earlier, it was noted that with movable contact arm 52b of stepping relay 52 moved to contact 523, the solenoid of relay 94 was energized, which closed switch 94a, provided that the movable arm 54h of stepping relay 54 had not moved so as to lopen the circuit between conductor 96 and line conductor L1. On three complete passes of movable arm 50h of relay 50 (p-roducing three movements of arm 52h and engagement of arm 52b with contact 52j), and if only three or a lesser number of veneer pieces have passed the moisture detector, then arm 54b still produces a closed circuit between conductor 96 and line conductor L1. This is an indication that the pieces are being overly dried if maximum production is to be obtained, and that a speed-up in dryer speed is needed.

Such a condition results in energizing of the solenoid of relay 94, closing of switch 94a, and the completion of a circuit from line conductor L1 -through switch 94a, conductor 110, normally closed switch 67b of time-delay relay 67, conductor 112, the solenoid of the time-delay relay, to line conductor L2. This energizes the solenoid of time-delay relay 67, `producing closing of its normally open switches 67C, 67d, and 67e, and opening of its normally closed switch 67a. Switch 6711 of the time-delay relay also opens, but only after the lapse of a predetermined time interval (to indicate the special nature of the switch, i.e., that it is a delayed-opening switch, it has Vbeen enclosed in a dotted outline in FIG. 2).

With reference now to FIG. l, at there is indicated a reversible electric motor, also referred to as a control motor (being part of lthe control means provided for controlling the speed of the conveyer). Motor 120 yis connected `by chain 122 to sprocket 30 and shaft 28.

Controlling running periods of motor 120 in either a forward or a reverse direction are the usual motor controls in motor control unit 124. Such control unit includes a solenoid or electrically operated device 126 (see FIG. 2) which is operable when energized to produce running of motor 120 in one direction (with such direction adjusting gear box 24 so as to produce a speed-up in the speed of the conveyer). Also part of the control unit is a solenoid or electrically operated device 128, which is operable when energized to produce running of motor 120 in the opposite direction (such direction adjusting gear box 24 so as to slow down the conveyer in the dryer).

Therefore, to obtain a faster conveyor speed in the dryer, solenoid 126 is energized, and the amount of change that occurs is determined by the length of time that solenoid 126 is energized and that motor 120 runs in the direction controlled by the solenoid. Conversely, solenoid 128 is energized to obtain a slower speed, and the amount of change that occurs is determined by the length of time that solenoid 128 is energized.

Switch 67e of the time-delay relay is a holding switch, and is operable to keep the solenoid of relay 67 energized, through delayed opening switch 6'7 b, upon the de-energizing of the solenoid of relay 94. Switch 67C of relay 67, when it closes, serves to reset stepping relay 54 and stepping relay 52, by completing a circuit from line conduct-or L1, through the switch, and conductors 130, 132, to resetting solenoid 54a (in the case of stepping relay 54), and by completing a circuit from line conductor L1 through conductors 130, and 134, to resetting solenoid 52d (in the case of stepping relay 52). (With these stepping relays, as with the other stepping relays discussed herein, the movable contact arms move back to their starting position on being reset, to prepare them for a subsequent cycle of operation). Switch 67a of relay 67, `when it opens7 isolates solenoid 50a of stepping relay 511 during resetting of the relay. Switch 67d when it closes completes a circuit from line conductor L1, through conductor 136, a movable contact arm 13361 of another stepping relay 138, a conductor 140, and solenoid 126, to line conductor L11, whereby solenoid 126 is energized and speed-up in dryer speed occurs.

Stepping relay 138 -is part of means provided for limiting the increase that may take place in the dryer speed at any one time of adjustment. On closing of switch 67e of time-delay relay 67, a circuit is also completed to line conductor L2 through switch 6711, conductor 142, and solenoid 13312 of the stepping relay. This energizes the solenoid, and with the solenoid energized, movable contact arm 133e of the stepping relay advances along one of the electrically joined contacts 138C in stepping relay 138. After three such advancements, electrically isolated contact 138d in the stepping relay is engaged, with the result that subsequent energizing 4of time-delay relay 67 is ineffective to produce energizing of solenoid 126 and speeding up of the dryer.

During the time that stepping relays 50 and 52 are counting off 105 veneer pieces, if an excessive number of wet pieces are detected and a slower speed is indicated, movable contact arm 5411 of stepping relay 54 shifts to a position engaging contact 54e. In the embodiment illustrated, this occurs after the detection of ve wet pieces. With contact 54e engaged, the solenoid of relay 72 becomes energized, producing closing of its normally open switch 72a and opening of switch 72b.

With closing of switch 72a, -a circuit is completed from line conductor L1 through the switch, conductor 144, normally closed delayed-opening switch 63b of time-delay relay 63, the solenoid of time-delay relay 63, conductor 146, and closed switch 158C of relay 158, to line conductor L2. Switch 6312 of time-delay relay 63 opens, but only after the expiration of a time interval (as in the case of delayed-opening switch 67b of relay 67). With the solenoid of relay 63 energized, switches 63C, 63d, and 63e of the relay close, and -switch 63a opens.

With opening of switch 63a, solenoid 50a of stepping relay 50 is electrically isolated, enabling stepping relay 50 to be reset. Switch 63C is a holding switch, and holds the solenoid of relay 63 energized, through delayedopening switch 63b. Switch 63e completes a circuit from line conductor L1, through solenoid 128 to line conductor L2. This energizes solenoid 128, and results in slowing down of the dryer.

Switch 63d when closed completes a circuit to line conductor L2, through conductor 1118, and resetting solenoid 52d of -stepping relay 52 and resetting solenoid 54a of stepping relay 54. Thus on slowdown of the dryer these stepping relays are reset. Closing of switch 63d also completes a circuit from line conductor L1, through conductor 149 and solenoid 56e of stepping relay 50 to line conductor L2, whereby stepping relay 52 is reset on slowdown of the dryer.

In the construction, the amount of time that delayedopening switch 67b of time-delay relay 67 and delayedopening switch 63b of time-delay relay 63 remain closed is the amount of running time required in the reversible control motor to produce the speed adjustment desired in the dryer. When these delayed-opening switches open, the control motor stops running. It will be noted that suitable resetting of the stepping relays has occurred on opening of the switches to permit a cycle of operation to be repeated.

In the event that movable arm 52b of stepping relay 52 (which counts the total passes made by the arm in relay 50) should move into engagement with contact 521, and at this time movable arm 54b of stepping relay 54 should be engaging electrically isolated contact 54d (had counted oi four wet pieces), then no change in dryer speed would immediately occur. Movable arm 50h of stepping relay 50 is then ena-bled to start another pass, and to start counting off another 35 veneer pieces. If during this count a wet piece of veneer is detected, such produces movement of arm Slt-b into engagement with contact 54e of relay 54. This results in energizing of relay 72 and slowing down of the dryer. Should no wet piece 'be detected, however, then arm 50h would complete its pass, and arm 52b would move into engagement with contact 52g of relay 52. When this happens, the solenoid of a relay 150 is energized, producing closing of its switches 15M, 150b. Switch 150b is a holding switch holding the relay energized. Switch 150a produces resetting of stepping relays S2 and 54, respectively, through energizing of their resetting solenoids 54a and 52d.

Manual control switches for adjusting dryer speed, through energizing either solenoid 126 or solenoid 128, to produce proper running direction in reversible motor 120, are indicated at 154 and 156.

With switch 154 closed, the solenoid of a relay 158 is energized, with closing of its switches 158a, 158b, and opening of switch 158C. With switch 158b closed, time-delay relay 67 is energized. This result in resetting of stepping relay 54 and stepping relay 52, through closing of switch 67C, and further results in energizing of solenoid 126 (through closing of switch 67d) and a yfaster speed in the dryer. With switch 158a closed, resetting of stepping relay 138 through energizing of its solenoid 138e occurs. Opening of switch 158e isolates solenoid 13811 of relay 138.

On closing of manual control switch 156, the solenoid of time-delay relay 63 is energized. This produces closing of its switch 63d and resetting of stepping relays 52 and 54. At the same time, a slowdown in dryer speed results from closing of switch 63e. Further, with switch 156 closed, a circuit is completed through a conductor 160 to the resetting solenoid 138e of stepping relay 138, causing this stepping relay to `be reset.

The operation of the apparatus will now be briefly described, although it should be fully clear from the above description of the invention. As sheets travel through the dryer, sample batches are counted out by stepping relays S0 and 52, which together are operable to count out (in the embodiment illustrated) pieces. At the same time that these pieces are being counted out, the wet pieces are counted by `the moisture detector and the stepping relay 54 in the circuit which it operates. If, at any time during the counting of 105 pieces, ve or more wet pieces are counted, then a circuit is completed producing slowdown of the dryer through energizing of the slowdown solenoid 128 in the motor control unit for the reversible control motor.

On the other hand, if during the counting of the 105 pieces three or a lesser number of wet pieces are counted, then this is an indication that the dryer is running too slowly. This produces speed-up of the dryer, through energizing of the speed-up solenoid 126 in the control unit for the reversible control motor.

In the event that exactly four wet pieces are counted, during the count of a 105-piece sample batch, then stepping relay 5t) is enabled to ystart counting another 35 pieces. If at any time one of these pieces is wet, then slowdown occurs. If none are wet, then the solenoid of relay is energized, the various stepping switches are reset, and another count of 105 pieces is undertaken.

It will be noted that, in the dryer apparatus contemplated, dryer speed is controlled automatically, with continuous testing performed on successive sheets of veneer traveling through the dryer, and with the results obtained from the testing controlling dryer speed. The testing of the sheets enables the proportion of wet to dry sheets to be determined. If at any time in a sample batch of sheets or pieces it is determined that too many wet pieces are present, dryer speed is adjusted immediately, to prevent further `accumulation of wet pieces.

The usual moisture detector has means for marking wet pieces. According to this invention, after these pieces are marked and deposited at the off-bearing end of the dryer, they are collected and subsequently may be passed through a dryer in a redry operation. Maximum production is possible, since the dryer is not used to dry all veneer pieces including the exceptional pieces in one pass.

The invention includes the method as well as the apparatus, by which maximum dryer production is realized.

While there has been described a specific embodiment of the invention, various modications land variations are possible without departing therefrom. It is intended to cover all such modifications and variations that would be apparent to one skilled in the art, and that come within the scope ofthe appended claims.

I-t is claimed and desired to secure by Letters Patent:

1. In the drying of articles where such articles ilow continuously through a dryer, the method comprising testing at regular intervals the moisture content of the articles after they have completed a substantial portion of their travel through the dryer,

making a plurality of such tests and totalizing the results obtained to determine the proportion of wet to dry articles,

after such totalizing Iof the results adjusting the ilow speed of `articles through the dryer to produce a slower speed where the proportion of wet -to dry articles is high, and

`to produce a faster speed where the proportion of wet to dry articles is low.

2. In the drying of articles where such articles flow continuously through a dryer, the method comprising establishing a satisfactory moisture level for the articles,

testing at regular intervals the moisture content of successive articles after they have completed a substantial portion of their travel through the dryer,

said testing being done to determine if the articles have moisture contents above or below said satisfactory level,

making a plurality of such tests and totalizing the results obtained to determine the proportion of articles having moisture contents falling above to articles having moisture contents falling below said satisfac` tory level,

after such totalizing of the results adjusting the ow speed of articles through the dryer to produce a slower speed where said proportion is above a predetermined ratio, and

to produce a faster `speed where said proportion is below a predetermined ratio.

3. In the drying of a series of wooden shee-ts where such sheets ilow continuously through a dryer, the method comprising dividing the series of sheets owing through the dryer into successive sample batches,

testing successive sheets of each sample batch to determine the proportion of wet to dry sheets,

said testing being done after the sheets have completed a substantial portion of their travel through the dryer, totalizing the results obtained in each sample batch to determine the proportion of wet to dry sheets, and after such totalizing of the results and after each sample batch of sheets has been tested adjusting the ilow speed of sheets through the dryer to produce a slower speed Where the proportion of wet to dry sheets is high and to produce a faster speed where the proportion of wet to dry sheets is low,

said `adjusting being omitted w-here the proportion of wet to dry sheets is in a predetermined range.

4. In the drying of a series of wooden sheets where it) such sheets ow continuously through a dryer, the method comprising establishing a satisfactory moisture level for the sheets,

dividing the series of sheets lowing through the dryer into successive sample batches, testing successive sheets in each batch of sheets llowing through the dryer to determine if the sheets have moisture contents above or below said level,

totalizing the results obtained in the testing of sheets to determine the total number of sheets with moisture contents above said level, immediately adjusting the flow speed of sheets through the dryer to produce a slower speed upon a predetermined number of sheets in a batch of sheets being found to have moisture contents above said level, and adjusting the How speed of sheets through the dryer to produce a faster speed when, upon the completion of the testing of sheets in a batch, it is found that a predetermined number of sheets have moisture contents below said level. 5. The method of claim 4, wherein adjustments to produce a faster ow speed are made in steps, when it is found that in successive batches of sheets a predetermined number of sheets have moisture contents below said level.

6. In a dryer having a conveyer and adjustable conveyer drive means connected to the conveyer which is adjustable to speed up and slow down the conveyer, said dryer being operable to dry articles moved by said conveyer through the dryer, mechanism operatively connected to the conveyer drive means for controlling the speed of the conveyer in the dryer comprising rst article-counting means for counting successive articles moved by the conveyer through the dryer,

moisture-detector means for detecting the amount of moisture in successive articles moved by the conveyer through the dryer,

second article-counting means for counting articles having moistures with a certain range as determined by said moisture-detector means, and

means responsive to said rst and second article-counting means operable to speed up and slow down said conveyer depending upon the proportion of articles counted by said second article-counting means t0 articles counted by said first article-counting means.

7. In a dryer having a conveyer and adjustable conveyer drive means connected to the conveyer which is adjustable to speed up and slow down the conveyer, said dryer being operable to dry articles moved by said conveyer through the dryer,

moisture-detector means operable to classify articles as wet and dry articles with such classification depending upon their moisture contents, first article-counting means for counting successive articles moved by the conveyer through the dryer,

second article-counting means for counting articles in one of the classifications produced by said moisturedetector means, and

means responsive to said rst and second article-counting means operatively connected to said conveyer drive means operable to speed up said conveyer when the proportion of wet to dry articles falls below a predetermined ratio,

said means being further operable to slow down said conveyer when the proportion of wet to dry articles falls above said predetermined ratio.

8. In a dryer having a conveyer and adjustable conveyer drive means connected to the conveyer which is adjustable to speed up and slow down the conveyer, said dryer being operable to dry articles moved by the conveyer through the dryer,

recurrently operating lirst counter means for counting off in succession sample batches of articles,

each of said sample batches comprising plural successive articles moved through the dryer by the conveyer,

moisture-detector means operable to classify articles as wet and dry articles with such classification depending upon their moisture contents,

recurrently operating second counter means operable to initiate a count of articles classified as wet articles by said moisture-detector means at the start of a count of a sample batch of articles by said first counter means,

means responsive to said second counter means and operatively connected to said conveyer drive means operable to produce a slowdown of said conveyer upon a predetermined number of articles classied as wet articles being counted by said second counter means, and

means responsive to said rst and second counter means and operatively connected to said conveyer drive means operable to speed up said conveyer at the end of a count of a sample batch of articles upon less than a predetermined number of articles classiied as wet articles being counted by said second counter means.

9. In combination with a dryer having a conveyer operable to move articles therethrough and means for driving the conveyer,

power-operated means for adjusting the driven speed of said conveyer by said motor, said means comprising a reversible control motor,

means connecting the reversible control motor to said means for driving the conveyer whereby operation of the control motor in one direction slows down the conveyer and operation of the control motor in the opposite direction speeds up the conveyer,

means controlling operation of said reversible control motor sensitive to the proportion of wet and dry articles moving through the conveyer, said last-mentioned means comprising a moisture detector operable to classify articles as wet and dry with classification depending upon their moisture content,

said moisture-detector means producing a control pulse upon classifying an article as a wet article,

an article counter comprising a first stepping switch advanced in steps into an actuating position in response to successive articles traveling through the dryer on the conveyer,

a second stepping switch advanced in steps into an actuating position,

means connecting said second stepping switch and said moisture detector whereby the former is advanced in response to successive control pulses produced by the moisture detector, and

means connecting said first an-d second stepping switches to said reversible control motor whereby operation of said motor occurs in one direction on advancement of said rst stepping switch to its actuating position and operation of said motor occurs in the opposite direction on advancement of said second stepping switch to its actuating position.

10. A veneer dryer comprising a conveyer for moving veneer to be dried,

adjustable conveyer drive means connected to the con veyer for driving the conveyer which is adjustable to speed up and slow down the conveyer,

a reversible control motor operatively connected to said adjustable drive means,

iirst and second electrically operated control devices operable when one is energized to cause said control motor to run in one direction and when the other is energized to cause said control motor to run in the opposite direction,

a pair of stepping switches,

a sensor adapted to be actuated by veneer carried on the conveyer operatively connected to one of said stepping switches for producing step-wise advancement of the switch upon actuation of the sensor,

a moisture detector adapted to be actuated by wet veneer and means operatively connecting said moisture detector and the other of said stepping switches producing step-wise advancement upon actuation of said moisture detector, and

means connecting said one and said other of said stepping switches to said first and second electricallyoperated control devices whereby they control the operation of said reversible control motor.

References Cited by the Examiner UNITED STATES PATENTS 1,926,292 9/1933 Kruse 34-52 2,087,860 7/1937 Nichols 23S-98.4 2,244,722 6/1941 Norcross 34-52 2,543,790 3/1951 Maher et al. 235-98 2,942,352 6/ 1960 Eicken-Estienne 34-52 WILLIAM F. ODEA, Primary Exmniner.

NORMAN YUDKOFF, Examiner. 

1. IN THE DRYING OF ARTICLES WHERE SUCH ARTICLES FLOW CONTINUOUSLY THROUGH A DRYER, THE METHOD COMPRISING TESTING AT REGULAR INTERVALS THE MOISTURE CONTENT OF THE ARTICLES AFTER THEY HAVE COMPLETED A SUBSTANTIAL PORTION OF THEIR TRAVEL THROUGH THE DRYER, MAKING A PLURALITY OF SUCH TESTS AND TOTALIZING THE RESULTS OBTAINED TO DETERMINE THE PROPORTION OF WET TO DRY ARTICLES, AFTER SUCH TOTALIZING OF THE RESULTS ADJUSTING THE FLOW SPEED OF ARTICLES THROUGH THE DRYER TO PRODUCE A SLOWER SPEED WHERE THE PROPORTION OF WET TO DRY ARTICLES IS HIGH, AND TO PRODUCE A FASTER SPEED WHERE THE PROPORTION OF WET TO DRY ARTICLES IS LOW. 